The proposed work includes studies on the effects of various ophthalmic drugs on the fluid permeability of the isolated rabbit ciliary epithelium, as measured with a small hydrostatic pressure head across the membrane. Other studies on the living rabbit eye will measure aqueous humor formation and pseudofacility, and correlation will be made between the in vitro and in vivo data. The data will be subjected to analysis to further determine the drug effects on parameters which cannot be directly measured, such as the pressure index of the capillaries. By using this in vitro and in vivo approach it will be possible to describe the effects of drugs on the components of aqueous formation. Expansion of the in vivo studies, using non-invasive techniques, to rhesus monkey eyes will allow a comparison to human data. The population of monkeys will be stable, and reproducible data will be obtained to act as a base-line for drug effects to be discerned. Iris phophilipid metabolism will be determined as a function of applied drugs, especially as these relate to membrane permeability changes. Drug effects on outflow pathways from the eye, as delineated by tracer studies, will be continued to identify the mode of drug action.